Systems and methods for encapsulating electronics in a mountable device

ABSTRACT

A mountable device includes a bio-compatible structure embedded in a polymer that defines at least one mounting surface. The bio-compatible structure includes an electronic component having electrical contacts, sensor electrodes, and electrical interconnects between the sensor electrodes and the electrical contacts. The bio-compatible structure is fabricated such that it is fully encapsulated by a bio-compatible material, except for the sensor electrodes. In the fabrication, the electronic component is positioned on a first layer of bio-compatible material and a second layer of bio-compatible material is formed over the first layer of bio-compatible material and the electronic component. The electrical contacts are exposed by removing a portion of the second layer, a conductive pattern is formed to define the sensor electrodes and electrical interconnects, and a third layer of bio-compatible material is formed over the conductive pattern. The sensor electrodes are exposed by removing a portion of the third layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/851,290, filed Mar. 27, 2013, which is currently pending.The entire disclosure contents of this application are herewithincorporated by reference into the present application.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

A mountable device may be configured to monitor health-relatedinformation based on at least one analyte detected from a user wearingthe mountable device. In the instance where the mountable device is aneye-mountable device, the eye-mountable device may be in the form of acontact lens that includes a sensor apparatus configured to detect oneor more analytes. The sensor apparatus may monitor health-relatedinformation of a user of the eye-mountable device, such as a glucoselevel. Further, the sensor apparatus may monitor various other types ofhealth-related information.

SUMMARY

In one aspect, an example mountable device is disclosed. The mountabledevice includes: a polymer that defines at least one mounting surface ofthe mountable device; and a bio-compatible structure embedded in thepolymer. The bio-compatible structure includes an electronic componentthat has electrical contacts on a contact surface thereof, sensorelectrodes, and electrical interconnects between the sensor electrodesand the electrical contacts, and a bio-compatible material fullyencapsulates the bio-compatible structure except for the sensorelectrodes. The sensor electrodes are disposed on a surface of thebio-compatible material that is substantially flush with the contactsurface of the electronic component.

In another aspect, an example method for fabricating a mountable deviceis disclosed. The method involves fabricating a bio-compatible structurethat includes an electronic component and a conductive pattern, in whichthe electronic component has a first surface and a second surfaceopposite the first surface and includes electrical contacts on thesecond surface. Fabricating the bio-compatible structure involves:forming a first layer of a bio-compatible material; positioning thefirst surface of the electronic component on the first layer of thebio-compatible material; forming a second layer of the bio-compatiblematerial over the first layer of the bio-compatible material and thesecond surface of the electronic component; exposing the electricalcontacts on the second surface of the electronic component by removing aportion of the second layer of the bio-compatible material; afterexposing the electrical contacts, forming the conductive pattern todefine sensor electrodes on the second layer of the bio-compatiblematerial and electrical interconnects between the sensor electrodes andthe electrical contacts; forming a third layer of the bio-compatiblematerial over the conductive pattern; exposing the sensor electrodes byremoving a portion of the third layer of the bio-compatible material;and surrounding the bio-compatible structure with a polymer. The polymerdefines at least one mounting surface of the mountable device.

In yet another aspect, an example method is disclosed. The methodinvolves: forming a first layer of a bio-compatible material;positioning, on the first layer of the bio-compatible material, anelectronic component that has a first surface and a second surfaceopposite the first surface and includes first electrical contacts andsecond electrical contacts on the second surface, such that the firstsurface is in contact with the first layer of the bio-compatiblematerial; forming a second layer of the bio-compatible material over thefirst layer of the bio-compatible material and the second surface of theelectronic component; removing a portion of the second layer of thebio-compatible material so as to expose the first electrical contactsand the second electrical contacts on the second surface of theelectronic component; forming a conductive pattern that defines sensorelectrodes and an antenna on the second layer of the bio-compatiblematerial, first electrical interconnects between the sensor electrodesand the first electrical contacts, and second electrical interconnectsbetween the antenna and the second electrical contacts; forming a thirdlayer of the bio-compatible material over the conductive pattern;removing a portion of the third layer of the bio-compatible material soas to expose the sensor electrodes; and annealing the first, second, andthird layers of the bio-compatible material to provide a bio-compatiblestructure that includes the electronic component and the conductivepattern. The bio-compatible material fully encapsulates thebio-compatible structure except for the sensor electrodes.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system that includes aneye-mountable device in wireless communication with an external reader.

FIG. 2A is a bottom view of an example eye-mountable device.

FIG. 2B is a side view of the example eye-mountable device of FIG. 2A.

FIG. 2C is a side cross-section view of the example eye-mountable deviceof FIG. 2A mounted to a corneal surface of an eye.

FIG. 2D is an enlarged partial view of the cross-section of the exampleeye-mountable device shown in FIG. 2C.

FIGS. 3A-3K show stages of fabricating an example bio-compatiblestructure in which an electronics module is encapsulated in abio-compatible material.

FIG. 4A is a flowchart of an example process for fabricating a mountabledevice.

FIG. 4B is a flowchart of an example process for fabricating abio-compatible structure.

FIG. 5 depicts a computer-readable medium configured according to anexample embodiment.

DETAILED DESCRIPTION

The following detailed description describes various features andfunctions of the disclosed systems and methods with reference to theaccompanying figures. In the figures, similar symbols typically identifysimilar components, unless context dictates otherwise. The illustrativeembodiments described herein are not meant to be limiting. It will bereadily understood that certain aspects of the present disclosure may bearranged and combined in a wide variety of different configurations, allof which are contemplated herein.

I. Overview

A mountable device may be configured to monitor health-relatedinformation based on at least one analyte detected from a user wearingthe mountable device. The mountable device may include a sensingplatform configured to detect the at least one analyte. The sensingplatform may include a sensor apparatus, control electronics, and anantenna, and may be at least partially embedded in a polymeric materialthat defines at least one mounting surface of the mountable device. Thecontrol electronics operate the sensor apparatus to perform readingsindicative of concentrations of an analyte and operate the antenna towirelessly communicate the readings to an external reader.

In some examples, the mountable device could be an eye-mountable device.The eye-mountable device may be in the form of a round lens configuredto mount to a corneal surface of an eye. The sensing platform may beembedded near the periphery of the eye-mountable device to avoidinterference with incident light received closer to the central regionof the cornea. As used throughout this disclosure, the anterior side ofthe eye-mountable device refers to the outward-facing side of theeye-mountable device that does not teach the eye of the wearer, whereasthe posterior side of the eye-mountable device refers to theinward-facing side of the eye-mountable device that touches the eye ofthe wearer.

The sensor apparatus may be an electrochemical amperometric sensor,which measures a concentration of an analyte by measuring a currentgenerated through electrochemical oxidation or reduction reactions ofthe analyte. The analyte diffuses to a working electrode of the sensorand is adsorbed on the working electrode. An electrochemical reactionthen occurs. A reduction reaction occurs when electrons are transferredfrom the working electrode to the analyte, whereas an oxidation reactionoccurs when electrons are transferred from the analyte to the workingelectrode. The direction of electron transfer is dependent upon theelectrical potentials applied to the working electrode. The response(i.e., analytical signal) of the sensor is the generated current thatflows between the working electrode and a counter electrode and/orreference electrode, which is used to complete a circuit with theworking electrode. When the working electrode is appropriately biased,the generated current can be proportional to the reaction rate, so as toprovide a measure of the concentration of the analyte surrounding theworking electrode.

In some examples, the sensing platform is in the form of abio-compatible structure. The bio-compatible structure may beencapsulated in a bio-compatible material, except for the sensorelectrodes of the electrochemical sensor. The bio-compatible materialcan protect the electronics in the sensing platform from fluids or othermaterials in the surrounding environment without triggering an immuneresponse, and the analyte can reach the exposed sensor electrodes.

The bio-compatible structure may be fabricating by positioning anelectronic component on a first layer of bio-compatible material, andforming one or more layers of bio-compatible material over theelectronic component and over a conductive pattern that defines thesensor electrodes, antenna, and respective electrical interconnects torespective electrical contacts on the electrical component. Then, aportion of the bio-compatible material over the sensor electrodes may beremoved, for example, by etching.

II. Example Sensing Platform

FIG. 1 is a block diagram of a system 100 that includes an eye-mountabledevice 110 in wireless communication with an external reader 120. Theeye-mountable device 110 may be a polymeric material that may beappropriately shaped for mounting to a corneal surface and in which asensing platform is at least partially embedded. The sensing platformmay include a power supply 140, a controller 150, bio-interactiveelectronics 160, and an antenna 170.

In some example embodiments, the sensing platform may be positioned awayfrom the center of the eye-mountable device 110 and thereby avoidinterference with light transmission to the central, light-sensitiveregion of the eye. For example, where the eye-mountable device 110 isshaped as a curved disk, the sensing platform may be embedded around theperiphery (e.g., near the outer circumference) of the disk. In otherexample embodiments, the sensing platform may be positioned in or nearthe central region of the eye-mountable device 110. For example,portions of the sensing platform may be substantially transparent toincoming visible light to mitigate interference with light transmissionto the eye. Moreover, in some embodiments, the bio-interactiveelectronics 160 may include a pixel array 164 that emits and/ortransmits light to be received by the eye according to displayinstructions. Thus, the bio-interactive electronics 160 may optionallybe positioned in the center of the eye-mountable device so as togenerate visual cues perceivable to a wearer of the eye-mountable device110, such as displaying information (e.g., characters, symbols, flashingpatterns, etc.) on the pixel array 164.

The power supply 140 is configured to harvest ambient energy to powerthe controller 150 and bio-interactive electronics 160, and may includean energy harvesting antenna 142 and/or solar cells 144. Theenergy-harvesting antenna 142 may capture energy from incident radioradiation. The solar cells 144 may comprise photovoltaic cellsconfigured to capture energy from incoming ultraviolet, visible, and/orinfrared radiation.

A rectifier/regulator 146 may be used to condition the captured energyto a stable DC supply voltage 141 at a level suitable for operating thecontroller, and then supply the voltage to the controller 150. Therectifier/regulator 146 may include one or more energy storage devicesto mitigate high frequency variations in the ambient energy gatheringantenna 142 and/or solar cell(s) 144. For example, one or more energystorage devices (e.g., a capacitor or an inductor) may be connected inparallel across the outputs of the rectifier 146 to regulate the DCsupply voltage 141 and may be configured to function as a low-passfilter.

The controller 150 is configured to execute instructions to operate thebio-interactive electronics 160 and the antenna 170. The controller 150includes logic circuitry configured to operate the bio-interactiveelectronics 160 so as to interact with a biological environment of theeye-mountable device 110. The interaction could involve the use of oneor more components, such an analyte bio-sensor 162 in thebio-interactive electronics 160, to obtain input from the biologicalenvironment. Additionally or alternatively, the interaction couldinvolve the use of one or more components, such as a pixel array 164, toprovide an output to the biological environment.

In one example, the controller 150 includes a sensor interface module152 that is configured to operate the analyte bio-sensor 162. Theanalyte bio-sensor 162 may be, for example, an amperometricelectrochemical sensor that includes a working electrode and a referenceelectrode driven by a sensor interface. A voltage is applied between theworking and reference electrodes to cause an analyte to undergo anelectrochemical reaction (e.g., a reduction and/or oxidation reaction)at the working electrode. The electrochemical reaction generates anamperometric current that can be measured through the working electrode.The amperometric current can be dependent on the analyte concentration.Thus, the amount of the amperometric current that is measured throughthe working electrode can provide an indication of analyteconcentration. In some embodiments, the sensor interface module 152 canbe a potentiostat configured to apply a voltage difference betweenworking and reference electrodes while measuring a current through theworking electrode.

In some instances, a reagent may also be included to sensitize theelectrochemical sensor to one or more desired analytes. For example, alayer of glucose oxidase (“GOD”) proximal to the working electrode cancatalyze glucose oxidation to generate hydrogen peroxide (H₂O₂). Thehydrogen peroxide can then be electro-oxidized at the working electrode,which releases electrons to the working electrode, resulting in anamperometric current that can be measured through the working electrode.

The current generated by either reduction or oxidation reactions isapproximately proportionate to the reaction rate. Further, the reactionrate is dependent on the rate of analyte molecules reaching theelectrochemical sensor electrodes to fuel the reduction or oxidationreactions, either directly or catalytically through a reagent. In asteady state, where analyte molecules diffuse to the electrochemicalsensor electrodes from a sampled region at approximately the same ratethat additional analyte molecules diffuse to the sampled region fromsurrounding regions, the reaction rate is approximately proportionate tothe concentration of the analyte molecules. The current measured throughthe working electrode thus provides an indication of the analyteconcentration.

The controller 150 may also include a display driver module 154 foroperating a pixel array 164. The pixel array 164 is an array ofseparately programmable light transmitting, light reflecting, and/orlight emitting pixels arranged in rows and columns. The individual pixelcircuits can optionally include liquid crystal technologies,microelectromechanical technologies, emissive diode technologies, etc.to selectively transmit, reflect, and/or emit light according toinformation from the display driver module 154. Such a pixel array 164may also include more than one color of pixels (e.g., red, green, andblue pixels) to render visual content in color. The display drivermodule 154 can include, for example, one or more data lines providingprogramming information to the separately programmed pixels in the pixelarray 164 and one or more addressing lines for setting groups of pixelsto receive such programming information. Such a pixel array 164 situatedon the eye can also include one or more lenses to direct light from thepixel array to a focal plane perceivable by the eye.

The controller 150 may also include a communication circuit 156 forsending and/or receiving information via the antenna 170. Thecommunication circuit 156 may include one or more oscillators, mixers,frequency injectors, or the like to modulate and/or demodulateinformation on a carrier frequency to be transmitted and/or received bythe antenna 170. In some example embodiments, the eye-mountable device110 is configured to indicate an output from a bio-sensor by modulatingan impedance of the antenna 170 in a manner that is perceivable by theexternal reader 120. For example, the communication circuit 156 cancause variations in the amplitude, phase, and/or frequency ofbackscatter radiation from the antenna 170, and such variations may thenbe detected by the reader 120.

The controller 150 is connected to the bio-interactive electronics 160and the antenna 170 via interconnects 151. The interconnects 151 maycomprise a patterned conductive material (e.g., gold, platinum,palladium, titanium, copper, aluminum, silver, metals, any combinationsof these, etc.).

It is noted that the block diagram shown in FIG. 1 is described inconnection with functional modules for convenience in description.However, embodiments of the eye-mountable device 110 can be arrangedwith one or more of the functional modules (“sub-systems”) implementedin a single chip, integrated circuit, and/or physical component.

Additionally or alternatively, the energy harvesting antenna 142 and thecommunication antenna 170 can be implemented in the same, dual-purposeantenna. For example, a loop antenna can both harvest incident radiationfor power generation and communicate information via backscatterradiation.

The external reader 120 includes an antenna 128 (or group of more thanone antennae) to send and receive wireless signals 171 to and from theeye-mountable device 110. The external reader 120 also includes acomputing system with a processor 126 in communication with a memory122. The memory 122 is a non-transitory computer-readable medium thatcan include, without limitation, magnetic disks, optical disks, organicmemory, and/or any other volatile (e.g. RAM) or non-volatile (e.g. ROM)storage system readable by the processor 126. The memory 122 includes adata storage 123 to store indications of data, such as sensor readings(e.g., from the analyte bio-sensor 162), program settings (e.g., toadjust behavior of the eye-mountable device 110 and/or external reader120), etc. The memory 122 also includes program instructions 124 forexecution by the processor 126. For example, the program instructions124 may cause the external reader 120 to provide a user interface thatallows for retrieving information communicated from the eye-mountabledevice 110 (e.g., sensor outputs from the analyte bio-sensor 162). Theexternal reader 120 may also include one or more hardware components foroperating the antenna 128 to send and receive the wireless signals 171to and from the eye-mountable device 110. For example, oscillators,frequency injectors, encoders, decoders, amplifiers, and filters candrive the antenna 128 according to instructions from the processor 126.

The external reader 120 may be a smart phone, digital assistant, orother portable computing device with wireless connectivity sufficient toprovide the wireless communication link 171. The external reader 120 mayalso be implemented as an antenna module that can be plugged in to aportable computing device, such as in an example where the communicationlink 171 operates at carrier frequencies not commonly employed inportable computing devices. In some instances, the external reader 120is a special-purpose device configured to be worn relatively near awearer's eye to allow the wireless communication link 171 to operateusing little or low power. For example, the external reader 120 can beintegrated in a piece of jewelry such as a necklace, earing, etc. orintegrated in an article of clothing worn near the head, such as a hat,headband, etc.

In an example where the eye-mountable device 110 includes an analytebio-sensor 162, the system 100 can be operated to monitor the analyteconcentration in tear film on the surface of the eye. To perform areading with the system 100 configured as a tear film analyte monitor,the external reader 120 can emit radio frequency radiation 171 that isharvested to power the eye-mountable device 110 via the power supply140. Radio frequency electrical signals captured by the energyharvesting antenna 142 (and/or the communication antenna 170) arerectified and/or regulated in the rectifier/regulator 146 and aregulated DC supply voltage 147 is provided to the controller 150. Theradio frequency radiation 171 thus turns on the electronic componentswithin the eye-mountable device 110. Once turned on, the controller 150operates the analyte bio-sensor 162 to measure an analyte concentrationlevel. For example, the sensor interface module 152 can apply a voltagebetween a working electrode and a reference electrode in the analytebio-sensor 162. The applied voltage can be sufficient to cause theanalyte to undergo an electrochemical reaction at the working electrodeand thereby generate an amperometric current that can be measuredthrough the working electrode. The measured amperometric current canprovide the sensor reading (“result”) indicative of the analyteconcentration. The controller 150 can operate the antenna 170 tocommunicate the sensor reading back to the external reader 120 (e.g.,via the communication circuit 156).

In some embodiments, the system 100 can operate to non-continuously(“intermittently”) supply energy to the eye-mountable device 110 topower the controller 150 and electronics 160. For example, radiofrequency radiation 171 can be supplied to power the eye-mountabledevice 110 long enough to carry out a tear film analyte concentrationmeasurement and communicate the results. For example, the supplied radiofrequency radiation can provide sufficient power to apply a potentialbetween a working electrode and a reference electrode sufficient toinduce electrochemical reactions at the working electrode, measure theresulting amperometric current, and modulate the antenna impedance toadjust the backscatter radiation in a manner indicative of the measuredamperometric current. In such an example, the supplied radio frequencyradiation 171 can be considered an interrogation signal from theexternal reader 120 to the eye-mountable device 110 to request ameasurement. By periodically interrogating the eye-mountable device 110(e.g., by supplying radio frequency radiation 171 to temporarily turnthe device on) and storing the sensor results (e.g., via the datastorage 123), the external reader 120 can accumulate a set of analyteconcentration measurements over time without continuously powering theeye-mountable device 110.

FIG. 2A is a bottom view of an example eye-mountable device 210. FIG. 2Bis an aspect view of the example eye-mountable device 210. It is notedthat relative dimensions in FIGS. 2A and 2B are not necessarily toscale, but have been rendered for purposes of explanation only indescribing the arrangement of the example eye-mountable device 210.

The eye-mountable device 210 may include a polymeric material 220, whichmay be a substantially transparent material to allow incident light tobe transmitted to the eye. The polymeric material 220 may include one ormore bio-compatible materials similar to those employed to form visioncorrection and/or cosmetic contact lenses in optometry, such aspolyethylene terephthalate (“PET”), polymethyl methacrylate (“PMMA”),polyhydroxyethylmethacrylate (“polyHEMA”), silicone hydrogels, or anycombinations of these. Other polymeric materials may also be envisioned.The polymeric material 220 may include materials configured tomoisturize the corneal surface, such as hydrogels and the like. In someembodiments, the polymeric material 220 is a deformable (“non-rigid”)material to enhance wearer comfort.

To facilitate contact-mounting, the eye-mountable device 210 maycomprise a concave surface 226 configured to adhere (“mount”) to amoistened corneal surface (e.g., by capillary forces with a tear filmcoating the corneal surface). The bottom view in FIG. 2A faces theconcave surface 226. While mounted with the concave surface against theeye, a convex surface 224 of eye-mountable device 210 is formed so asnot to interfere with eye-lid motion while the eye-mountable device 210is mounted to the eye. From the bottom view shown in FIG. 2A, an outerperiphery 222, near the outer circumference of the eye-mountable device210 has a concave curve shape, whereas a central region 221, near thecenter of the eye-mountable device 210, has a convex curve shape.

The eye-mountable device 210 can have dimensions similar to a visioncorrection and/or cosmetic contact lenses, such as a diameter ofapproximately 1 centimeter, and a thickness of about 0.1 to about 0.5millimeters. However, the diameter and thickness values are provided forexplanatory purposes only. In some embodiments, the dimensions of theeye-mountable device 210 may be selected according to the size and/orshape of the corneal surface of the wearer's eye. In some embodiments,the eye-mountable device 210 is shaped to provide a predetermined,vision-correcting optical power, such as provided by a prescriptioncontact lens.

A sensing platform 230 is embedded in the eye-mountable device 210. Thesensing platform 230 can be embedded to be situated near or along theouter periphery 222, away from the central region 221. Such a positionensures that the sensing platform 230 will not interfere with a wearer'svision when the eye-mountable device 210 is mounted on a wearer's eye,because it is positioned away from the central region 221 where incidentlight is transmitted to the eye-sensing portions of the eye. Moreover,portions of the sensing platform 230 can be formed of a transparentmaterial to further mitigate effects on visual perception.

The sensing platform 230 may be shaped as a flat, circular ring (e.g., adisk with a centered hole). The flat surface of the sensing platform 230(e.g., along the radial width) allows for mounting electronics such aschips (e.g., via flip-chip mounting) and for patterning conductivematerials to form electrodes, antenna(e), and/or interconnections. Thesensing platform 230 and the polymeric material 220 may be approximatelycylindrically symmetric about a common central axis. The sensingplatform 230 may have, for example, a diameter of about 10 millimeters,a radial width of about 1 millimeter (e.g., an outer radius 1 millimetergreater than an inner radius), and a thickness of about 50 micrometers.These dimensions are provided for example purposes only, and in no waylimit the present disclosure.

A loop antenna 270, controller 250, and bio-interactive electronics 260are included in the sensing platform 230. The controller 250 may be achip including logic elements configured to operate the bio-interactiveelectronics 260 and the loop antenna 270, and may be the same as orsimilar to the controller 150 discussed in connection with FIG. 1. Thecontroller 250 is electrically connected to the loop antenna 270 byinterconnects 257 also situated on the substrate 230. Similarly, thecontroller 250 is electrically connected to the bio-interactiveelectronics 260 by an interconnect 251. The interconnects 251, 257, theloop antenna 270, and any conductive electrodes (e.g., for anelectrochemical analyte bio-sensor, etc.) may be formed from any type ofconductive material and may be patterned by any process that be used forpatterning such materials, such as deposition or photolithography, forexample. The conductive materials patterned on the substrate 230 may be,for example, gold, platinum, palladium, titanium, carbon, aluminum,copper, silver, silver-chloride, conductors formed from noble materials,metals, or any combinations of these materials. Other materials may alsobe envisioned.

As shown in FIG. 2A, the bio-interactive electronics module 260 is on aside of the sensing platform 230 facing the convex surface 224. Wherethe bio-interactive electronics module 260 includes an analytebio-sensor, for example, mounting such a bio-sensor on the sensingplatform 230 to be close to the convex surface 224 allows the bio-sensorto sense analyte that has diffused through convex surface 224 or hasreached the bio-sensor through a channel in the convex surface 224(FIGS. 2C and 2D show a channel 272).

The loop antenna 270 is a layer of conductive material patterned alongthe flat surface of the substrate 230 to form a flat conductive ring.The loop antenna 270 may be the same as or similar to the antenna 170described in connection with FIG. 1. In some example embodiments, theloop antenna 270 does not form a complete loop. For example, the loopantenna 270 may include a cutout to allow room for the controller 250and bio-interactive electronics 260, as illustrated in FIG. 2A. However,in another example embodiment, the loop antenna 270 can be arranged as acontinuous strip of conductive material that wraps entirely around thesensing platform 230 one or more times. Interconnects between the endsof such a wound antenna (e.g., the antenna leads) can connect to thecontroller 250 in the sensing platform 230.

The sensing platform 230 may be a bio-compatible structure in which someor all of the components are encapsulated by a bio-compatible material.In one example, controller 250, interconnects 251, 257, bio-interactiveelectronics 260, and antenna 270 are fully encapsulated bybio-compatible material, except for the sensor electrodes in thebio-interactive electronics 260.

FIG. 2C is a side cross-section view of the example eye-mountableelectronic device 210 mounted to a corneal surface 284 of an eye 280.FIG. 2D is an enlarged partial view the cross-section of the exampleeye-mountable device shown in FIG. 2C. It is noted that relativedimensions in FIGS. 2C and 2D are not necessarily to scale, but havebeen rendered for purposes of explanation only in describing thearrangement of the example eye-mountable electronic device 210. Someaspects are exaggerated to allow for illustration and to facilitateexplanation.

The eye 280 includes a cornea 282 that is covered by bringing an uppereyelid 286 and a lower eyelid 288 together over the surface of the eye280. Incident light is received by the eye 280 through the cornea 282,where light is optically directed to light sensing elements of the eye280 to stimulate visual perception. The motion of the upper and lowereyelids 286, 288 distributes a tear film across the exposed cornealsurface 284 of the eye 280. The tear film is an aqueous solutionsecreted by the lacrimal gland to protect and lubricate the eye 280.When the eye-mountable device 210 is mounted in the eye 280, the tearfilm coats both the concave and convex surfaces 224, 226, providing aninner layer 290 (along the concave surface 226) and an outer layer 292(along the convex surface 224). The inner layer 290 on the cornealsurface 284 also facilitates mounting the eye-mountable device 210 bycapillary forces between the concave surface 226 and the corneal surface284. In some embodiments, the eye-mountable device 210 can also be heldover the eye 280 in part by vacuum forces against the corneal surface284 due to the curvature of the concave surface 226. The tear filmlayers 290, 292 may be about 10 micrometers in thickness and togetheraccount for about 10 microliters of fluid.

The tear film is in contact with the blood supply through capillaries inthe structure of the eye and includes many biomarkers found in bloodthat are analyzed to diagnose health states of an individual. Forexample, tear film includes glucose, calcium, sodium, cholesterol,potassium, other biomarkers, etc. The biomarker concentrations in tearfilm can be systematically different than the correspondingconcentrations of the biomarkers in the blood, but a relationshipbetween the two concentration levels can be established to map tear filmbiomarker concentration values to blood concentration levels. Forexample, the tear film concentration of glucose can be established(e.g., empirically determined) to be approximately one tenth thecorresponding blood glucose concentration. Although another ratiorelationship and/or a non-ratio relationship may be used. Thus,measuring tear film analyte concentration levels provides a non-invasivetechnique for monitoring biomarker levels in comparison to bloodsampling techniques performed by lancing a volume of blood to beanalyzed outside a person's body.

As shown in the cross-sectional views in FIGS. 2C and 2D, the sensingplatform 230 can be inclined so as to be approximately parallel to theadjacent portion of the convex surface 224. As described above, thesensing platform 230 is a flattened ring with an inward-facing surface232 (closer to the concave surface 226 of the polymeric material 220)and an outward-facing surface 234 (closer to the convex surface 224).The sensing platform 230 can include electronic components and/orpatterned conductive materials adjacent to either or both surfaces 232,234.

As shown in FIG. 2D, the bio-interactive electronics 260, the controller250, and the conductive interconnect 251 are mounted on theoutward-facing surface 234 such that the bio-interactive electronics 260are facing the convex surface 224. With this arrangement, thebio-interactive electronics 260 can receive analyte concentrations inthe tear film 292 through the channel 272. However, in other examples,the bio-interactive electronics 260 may be mounted on the inward-facingsurface 232 of the sensing platform 230 such that the bio-interactiveelectronics 260 are facing the concave surface 226.

III. Fabrication of an Example Bio-Compatible Structure

FIGS. 3A-3K illustrate stages in a process for fabricating abio-compatible structure, such as sensing platform 230. Theillustrations shown in FIG. 3A-3K are generally shown in cross-sectionalviews to illustrate sequentially formed layers developed to create thebio-compatible structure that encapsulates electronics. The layers canbe developed by microfabrication and/or manufacturing techniques suchas, for example, electroplating, photolithography, deposition, and/orevaporation fabrication processes and the like. The various materialsmay be formed according to patterns using photoresists and/or masks topattern materials in particular arrangements, such as to form wires,electrodes, connection pads, etc. Additionally, electroplatingtechniques may also be employed to coat an arrangement of electrodeswith a metallic plating. For example, an arrangement of conductivematerial formed by a deposition and/or photolithography process can beplated with a metallic material to create a conductive structure with adesired thickness. However, the dimensions, including relativethicknesses, of the various layers illustrated and described inconnection with FIGS. 3A-3K to create an encapsulated electronicsstructure are not illustrated to scale. Instead, the drawings in FIGS.3A-3K schematically illustrate the ordering of the various layers forpurposes of explanation only.

FIG. 3A illustrates a working substrate 302 coated with a first layer ofbio-compatible material 310. The working substrate 302 may be any flatsurface on which the layers of the encapsulated electronics structurecan be assembled. For example, the working substrate 302 may be a wafer(e.g., a silicon wafer) similar to those used in the fabrication ofsemiconductor device and/or microelectronics.

The first layer of bio-compatible material 310 may include a polymericmaterial such as parylene C (e.g., dichlorodi-p-xylylene), apolyethylene terephthalate (PET), a polydimethysiloxane (PDMS), othersilicone elastomers, and/or another bio-compatible polymeric material.Bio-compatibility refers generally to the ability of a material ordevice to co-exist with a biological host. Bio-compatible materials aregenerally those that do not bring about a host response (such as animmune response) that results in deleterious effects to either thebiological host or the material. In addition to being bio-compatible,the first layer of bio-compatible material 310 may be an electricallyinsulating material to isolate the encapsulated electronics from thesurrounding environment (e.g., from current-carrying particles and/orfluids).

The first layer of bio-compatible material 310 may be formed by amicrofabrication process such as vapor deposition on top of the workingsubstrate 302, and provides a surface on which the encapsulatedelectronics structure can be formed. The first layer of bio-compatiblematerial 310 may be deposited onto the working substrate 302 with asubstantially uniform thickness such that the surface of thebio-compatible material 310 opposite the working substrate 302 forms aflat surface. The first layer of bio-compatible material 310 maycomprise a thickness in the range of 1-50 micrometers, in one exampleembodiment.

FIG. 3B illustrates a chip 320 mounted to the first layer ofbio-compatible material 310. The chip 320 could include, for example,one or more integrated circuits (ICs) and/or one or more discreteelectronic components, such as a controller similar to the controller150 of FIG. 1. Heat, pressure, a pick-and-place tool, or a flip-chipbonder, for example, may be used to adhere a first surface 322 of thechip 320 to the first layer of bio-compatible material 310. Chip 320 hasa second surface 324 opposite the first surface 322 that includes firstelectrical contacts 326 and second electrical contacts 328.

As shown in FIG. 3C, a second layer of bio-compatible material 330 isthen formed over the first layer of bio-compatible material 310 and thechip 320. The second layer of bio-compatible material 330 is applieduntil the thickness of each of the portions of the layer formed directlyon top of the first layer 310 is substantially flush with the secondsurface 324 of the chip 320. The second layer of bio-compatible material330 may be evenly applied over both the exposed first layer as well asthe chip 320 that is placed on top of the first layer, such that aportion of the second layer 330 will form on top of the second surface324 of the chip 320. Such a portion of the second layer 330 formed ontop of the chip 320 is shown in FIG. 3C as portion 332.

As shown in FIG. 3D, a masking layer 335 may next be formed over theentire second layer 330 except for the portion 332 of the second layer330 that is formed on top of the second surface 324 of the chip 320. Insome examples, the masking layer 335 is a metal mask and may be madeusing photolithography or metal deposition (evaporation or sputtering).

The silicon wafer and materials on the wafer are then exposed to aplasma. The plasma may comprise a plasma asher, a reactive ion etcher,inductively coupled plasma, etc. The plasma will etch through anyexposed layers of bio-compatible material, through such layers down tothe working substrate 302; however, the plasma will not etch the maskinglayer or the chip 320. The masking layer thus serves to block theapplied plasma from etching anything directly underneath the maskinglayer. Various other components, such as the chip 320, may also serve asa mask to block the plasma from etching layers of bio-compatiblematerial that are directly under the components. Thus, as shown in FIG.3E, the plasma has etched away the portion 332 of the second layer ofbio-compatible material 330 down to the chip 320. The remaining portionsof the second layer of bio-compatible material 330 are protected fromplasma etching by the masking layer.

After application of plasma, the masking layer is removed, as shown inFIG. 3F. The masking layer may be removed by any number of methods. Forexample, if the masking layer is a metal mask, the removal may includeapplying a wet etch. What remains after application of the plasma andremoval of the masking layer is shown in FIG. 3F: a second layer ofbio-compatible material 330 having a top surface 334 that is level withthe exposed, second surface 324 of the chip 320.

Next, a conductive pattern be fabricated directly onto the second layerof bio-compatible material 330 the first electrical contacts 326, andthe second electrical contacts 328, as shown in FIG. 3G. For example,metal can be patterned onto the second layer of bio-compatible material330 to create components for an electrochemical bio-sensor circuitpowered by harvested radio frequency energy, similar to the exampleembodiment described above in connection with FIG. 1. In such an exampleembodiment, metal can be pattered to form components including sensorelectrodes 340, an antenna 350, and interconnects 352, 354. The sensorelectrodes 340 may include a working electrode and a reference and/orcounter electrode of an electrochemical sensor, for example, asdiscussed in connection with FIG. 1.

The antenna 350 may be a loop antenna suitable for receiving radiofrequency radiation harvested to provide a power supply to theelectronics. The antenna 350 may be, for example, a loop with a radiusof approximately 5 millimeters that is suitable for being arrangedaround the perimeter of an eye-mountable device, similar to the antennaillustrated and described in connection with FIGS. 1 and 2A-2D above.The sensor electrodes 340, the interconnects 352, 354, and the antenna350 can each be formed with a thickness of about 5 micrometers, forexample.

The interconnects 352, 354 can be wires formed by photolithography,evaporation, and/or electroplating. The interconnects 352 electricallyconnect the sensor electrodes 340 to the first electrical contacts 326on chip 320. The interconnects 354 electrically connect the antenna 350to the second electrical contacts on chip 328.

The second layer of bio-compatible material 330 may comprise sufficientstructural rigidity to be used as a substrate for assembling thecomponents. The components may be formed of conductive material such asplatinum, silver, gold, palladium, titanium, copper, chromium, nickel,aluminum, other metals or conductive materials, and combinationsthereof. Some example embodiments may employ a substantially transparentconductive material for at least some of the electronics circuitry(e.g., a material such as indium tin oxide).

In some example embodiments, one or more of the components patternedonto the first layer of bio-compatible material 310 may be a multi-layerarrangement that includes a seed layer (or adhesion layer) patterneddirectly on the second layer of bio-compatible material 330. Such a seedlayer can be used to adhere to both the bio-compatible material and thebulk of the metal structure that is patterned over the seed layer. Forexample, such a seed layer may be a material that adheres well to thebio-compatible material, and also serves as a guide to electroplate theremainder of the metal structure that forms the component.

Next, a third layer of bio-compatible material 360, shown in FIG. 3H, isformed over the assembled electronic components (i.e., the chip 320, thesensor electrodes 340, the antenna 350, and the interconnects 352, 354)and the remaining exposed second layer of bio-compatible material 330.The third layer of bio-compatible material 360 functions similar to thefirst layer of bio-compatible material 310 to create a bio-compatibleexterior surface and also electrically isolate the electronics from thesurrounding environment. In addition, the third layer of bio-compatiblematerial 360 structurally supports the assembled electronics and holdsthe various components in place. The third layer of bio-compatiblematerial 350 can stabilize the chip 320 by surrounding the chip 320 tofill gaps surrounding the chip 320 (and thereby prevent movement of thechip). In some examples, the deposition of the third layer ofbio-compatible material 360 results in a conformal coating over theassembled electronics. The third layer of bio-compatible material 360can have a thickness in the range of about 1 to 50 micrometers, forexample.

The third layer of bio-compatible material 360 can be formed of the sameor substantially similar material to the first and the second layers ofbio-compatible material 310, 330, or can optionally be a differentpolymeric material that is both bio-compatible and electricallyinsulating.

The third layer of bio-compatible material 360 is preferably depositedto create a continuous layer that spans the entirety of the assembledelectronics. The third layer of bio-compatible material 360 can span aregion that extends beyond a footprint of the assembled electronics. Asa result, the assembled electronics can be surrounded by portions of thethird layer of bio-compatible material 360 that rest directly on thesecond layer of bio-compatible material 330.

Next, as shown in FIG. 3I, a second masking layer 370 is applied on topof the third layer of bio-compatible material 360 in the shape of aflattened ring, for example, similar to the shape of the sensingplatform 230 illustrated and described in connection with FIG. 2A above.The second masking layer 370 covers the assembled electronics with theexception of at least a portion of the area directly above the sensorelectrodes 340. Again, in some examples, the masking layer 370 is ametal mask and may be made using photolithography or metal deposition(evaporation or sputtering).

The silicon wafer and materials on the wafer are then again exposed to aplasma. The plasma may comprise plasma asher, a reactive ion etcher,inductively coupled plasma, etc. The plasma will not etch through thesecond masking layer or exposed electronic components, such as thesensor apparatus 340. As shown in FIG. 3J, the plasma etches the exposedthird layer of bio-compatible material 360 leaving an opening 362. Theplasma may also etch any exposed layers of bio-compatible materialunderneath the third layer, all the way down to the working substrate302. The remaining portions of the third layer of bio-compatiblematerial 360 are protected from plasma etching by the second maskinglayer 370, and the remaining portions of the first and second layers maybe protected by components residing directly above those layers.

As shown in FIG. 3K, after application of plasma, the second maskinglayer 370 is removed. The second masking layer 370 may be removed by anynumber of methods. For example, if the second masking layer 370 is ametal, the removal may include applying a wet etch. What remains afterapplication of the plasma and removal of the second masking layer 370 isshown in FIG. 3K. Thus, the third layer of bio-compatible material 360covers the components except for an opening 362 over at least a portionof the sensor electrodes 340. Additionally, as discussed above, thesecond masking layer 370 was formed in a flattened ring shape and thusvarious layers of bio-compatible material that did not form the ringshape and did not have metal components directly above were removed bythe plasma. An example top view of a possible resulting ring shape ofthe device is shown as the sensing platform 230 in FIG. 2A.

While not specifically shown in FIGS. 3A-3K, some fabrication processesmay include forming a reagent layer proximal to the sensor electrodes340 (e.g., covering at least the working electrode in sensor electrodes340). The reagent layer may include a substance used to sensitize theelectrodes on the sensor electrodes 340 to a particular analyte. Forexample a layer including glucose oxidase may be applied to the sensorelectrodes 340 for detection of glucose.

To encapsulate the bio-compatible structure in the bio-compatiblematerial, the first layer 310, the second layer 330, and the third layer360 of the bio-compatible material can be annealed so that these layersseal together. The annealing can be performed by placing the entireassembled structure, including the working substrate 302, in an oven ata temperature sufficient to anneal the bio-compatible material in thefirst, second, and third layers 310, 330, 360. For example, parylene C(e.g., dichlorodi-p-xylylene) can be annealed at a temperature ofapproximately 150 to 200 degrees Celsius. Other bio-compatible polymericmaterials (such as PET, PDMS, etc.) may require higher or lowerannealing temperatures. Once cooled, the result is a bio-compatiblestructure in which a sealed, continuous layer of bio-compatible materialencapsulates the assembled electronics within, except for the sensorelectrodes 340.

Finally, the bio-compatible structure is released from the workingsubstrate 302. In one example, the bio-compatible structure can bepeeled away from the working substrate 302 following the annealingprocess. The encapsulated electronics structure may also be etched(e.g., application of an oxygen plasma) to remove excess bio-compatiblematerial prior to peeling away the structure. For example,bio-compatible material may at least partially wrap around the workingsubstrate 302 either during the deposition process or the annealingprocess or both.

The released bio-compatible structure is suitable for incorporation intoa biological environment, such as within an eye-mountable device or animplantable medical device, for example. Due to the encapsulatingbio-compatible material, the surrounding environment is sealed from theembedded electronics. For example, if the structure is implanted in abiological host, or placed in an eye-mountable device to be exposed totear fluid, the structure is able to be exposed to fluids of thebiological host (e.g., tear fluid, blood, etc.), because the entireexterior surface is coated with bio-compatible material, except that thesensor electrodes 340 are exposed to allow detection of one or moreanalytes in the fluid.

The description in FIGS. 3A-3K describes one example of a process forfabricating a bio-compatible structure that can be embedded in aneye-mountable device. However, the process described with reference toFIGS. 3A-3K may be employed to create bio-compatible structures forother applications, such as other implantable electronic medical deviceapplications. Such implantable electronic medical devices may include anantenna for communicating information (e.g., sensor results) and/orinductively harvesting energy (e.g., radio frequency radiation).Implantable electronic medical devices may also include electrochemicalsensors or they may include other electronic devices. The processdescribed with reference to FIGS. 3A-3K may be used to createbio-compatible structures suitable to be mounted on or in another partof the body. For example, bio-compatible structures may be mounted on orimplanted under the skin, such as in the abdomen or the upper arm, on atissue in the mouth, or in the brain to read electrical signals. Thebio-compatible structure described above may be applied to anyimplantable device that detects bio-markers.

The bio-compatible structure may include electronics that are configuredto perform functions in addition to, or as alternatives to, thosedescribed above. For example, the bio-compatible structure may include alight sensor, a temperature sensor, and/or other sensors useful fordetecting diagnostically relevant information in an ophthalmic and/orimplantable application. The electronics may, for example, obtain atemperature reading and then communicate the temperature information oruse the temperature information to modify a measurement procedure withthe electrochemical sensor. Moreover, the electronics may include acombination of capacitors, switches, etc., to regulate voltage levelsand/or control connections with other electronics modules.

FIG. 4A is a flowchart of an example method 400 for fabricating amountable device. The mountable device could be an eye-mountable device,such as eye-mountable device 110 shown in FIG. 1 or eye-mountable device210 shown in FIGS. 2A-2D.

The example method 400 involves fabricating a bio-compatible structurethat includes an electronic component and a conductive pattern (block402). The bio-compatible structure may be fabricated as described abovewith reference to FIGS. 3A-3K or described below with reference to FIG.4B.

The method then includes surrounding the bio-compatible structure with apolymer that defines at least one mounting surface (block 404). For aneye-mountable device, the polymer could be a transparent polymer and maytake the form of a disk or lens, as described with reference to FIGS.2A-2D. Thus, the polymer could define a concave surface that isconfigured to be mounted to a corneal surface. In other examples, thepolymer may define a surface configured to be mounted on the skin or ona tissue in the mouth. Other types of mounting surfaces are possible aswell.

The bio-compatible structure could be surrounded by the polymer invarious ways. In one example, a two-step injection molding process maybe used. In the first step, a first layer of the polymer is formed in amold, and the bio-compatible structure is placed on the first polymerlayer. In the second step, a second layer of the polymer is formed in amold so as to cover the bio-compatible structure on the first polymerlayer. Other methods for surrounding the bio-compatible structure withpolymer are possible as well.

FIG. 4B is a flowchart of an example method 410 for fabricating abio-compatible structure. Once fabricated, the bio-compatible structurecould be surrounded by a polymer that defines a mounting surface, asdescribed above with reference to FIG. 4A. Alternatively, thebio-compatible structure could be used in an implantable device or usedin other ways.

In the example method 410, the bio-compatible structure includes anelectronic component and a conductive pattern. The electronic componentcould be an integrated circuit, a discrete component (such as atransistor, resistor, or capacitor), or some other type of electroniccomponent. The electronic component may be the controller 150 describedwith reference to FIG. 1, for example. In this example, the electroniccomponent has a first surface and a second surface opposite the firstsurface and includes one or more electrical contacts on the secondsurface, such as the chip 320 described with reference to FIGS. 3B-3K.

The example method 410 includes forming a first layer of abio-compatible material (block 412). The first layer of thebio-compatible material may be the same as or similar to the first layerof bio-compatible material 310 as described with reference to FIGS.3A-3K, for example. In one example embodiment, the first layer ofbio-compatible material may be formed on a working substrate such as theworking substrate 302 as described with reference to FIGS. 3A-3K.

The method 410 further includes positioning the first surface of theelectronic component on the first layer of the bio-compatible material(block 414) and forming a second layer of the bio-compatible materialover the first layer of the bio-compatible material and the secondsurface of the electronic component (block 416). The second layer of thebio-compatible material may be formed similarly to the second layer ofbio-compatible material 330 as described with reference to FIGS. 3C-3K,for example.

The method 410 further includes exposing the electrical contacts on thesecond surface of the electronic component by removing a portion of thesecond layer of the bio-compatible material (block 418). Removing aportion of the second layer of the bio-compatible material may compriseapplying a metal mask to certain portions of the structure, such as themetal mask 335 described with reference to FIGS. 3D-3E, and thensubjecting the structure to a plasma to remove any exposed portions ofthe second layer.

The method 410 further includes, after exposing the electrical contacts,forming the conductive pattern (block 420). The conductive patterndefines at least sensor electrodes on the second layer of thebio-compatible material and electrical interconnects between the sensorelectrodes and the electrical contacts on the electronic component. Theconductive pattern may also define an antenna and electricalinterconnects between the antenna and additional electrical contacts onthe electronic component. The conductive pattern may define other typesof interconnects, wires, or conductive structures as well.

The conductive pattern may be formed using any of the methods describedherein. The sensor electrodes may be similar to the sensor electrodes340, as described with reference to FIG. 3G. The electricalinterconnects may be the same or similar to the interconnects 352 asdescribed with reference to FIG. 3G. Additional components may also bepositioned on the second polymer layer, such as the antenna 350 and theinterconnects 354 described above with reference to FIG. 3G.

The method includes forming a third layer of the bio-compatible materialover the conductive pattern (block 422). The third layer of thebio-compatible material may be similar to the layer of thebio-compatible material 360 described with reference to FIGS. 3H-3K.

The method 410 further includes exposing the sensor electrodes byremoving a portion of the third layer of the bio-compatible material(block 426). The portion of the third layer may be removed by exposureof the portion to a plasma, such as described with reference to FIGS.3J-3K.

Annealing processes may seal the three layers of bio-compatible materialto fully encapsulate the bio-compatible structure, as described above.

Additionally, the assembled encapsulated structure may be etched tocreate a ring-shaped structure, via a metal mask and ensuing plasmaapplication as described with reference to FIGS. 3I-3K. For example, theencapsulated structure may be etched to create a flattened-ring-shapesimilar to the ring-shaped sensing platform 230 shown and described inconnection with FIGS. 2A-2D above. The encapsulated structure may alsobe etched in another shape, such as a rectangle, a circle (e.g., adisc), an oval, etc. to create a generally flat structure in whichassembled electronics are encapsulated by sealed bio-compatiblematerial.

The bio-compatible structure can then be embedded into polymericmaterial of a mountable device. Where the bio-compatible structure isgiven a flattened-ring shape, the structure can be embedded around theperipheral region of a generally circular polymeric material shaped tobe contact-mounted to an eye, for example. Such a polymeric material mayhave, for example, a concave surface configured to be mounted over acorneal surface of an eye and a convex surface opposite the concavesurface configured to be compatible with eyelid motion while mounted tothe corneal surface. For example, a hydrogel material (or otherpolymeric material) can be formed around the bio-compatible structure inan injection molding process.

In other embodiments, the released encapsulated structure may beembedded into a mountable device to be mounted to another part of thebody, such as the skin or in the mouth, for example. For example,bio-compatible structures may be mounted on or implanted under the skin,such as in the abdomen or the upper arm, on a tissue in the mouth, or inthe brain to read electrical signals. The bio-compatible structuredescribed above may be applied to any implantable device that detectsbio-markers.

FIG. 5 depicts a computer-readable medium configured according to anexample embodiment. In example embodiments, the example system caninclude one or more processors, one or more forms of memory, one or moreinput devices/interfaces, one or more output devices/interfaces, andmachine-readable instructions that when executed by the one or moreprocessors cause the system to carry out the various functions, tasks,capabilities, etc., described above.

In some embodiments, the disclosed techniques can be implemented bycomputer program instructions encoded on a non-transitorycomputer-readable storage media in a machine-readable format, or onother non-transitory media or articles of manufacture. FIG. 5 is aschematic illustrating a conceptual partial view of an example computerprogram product that includes a computer program for executing acomputer process on a computing device, to perform any of the methodsdescribe herein.

In one embodiment, the example computer program product 500 is providedusing a signal bearing medium 502. The signal bearing medium 502 mayinclude one or more programming instructions 504 that, when executed byone or more processors may provide functionality or portions of thefunctionality described above with respect to FIGS. 1-4B. In someexamples, the signal bearing medium 502 can include a non-transitorycomputer-readable medium 506, such as, but not limited to, a hard diskdrive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape,memory, etc. In some implementations, the signal bearing medium 502 canbe a computer recordable medium 508, such as, but not limited to,memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations,the signal bearing medium 502 can be a communications medium 510, suchas, but not limited to, a digital and/or an analog communication medium(e.g., a fiber optic cable, a waveguide, a wired communications link, awireless communication link, etc.). Thus, for example, the signalbearing medium 502 can be conveyed by a wireless form of thecommunications medium 510.

The one or more programming instructions 504 can be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device is configured to provide variousoperations, functions, or actions in response to the programminginstructions 504 conveyed to the computing device by one or more of thecomputer readable medium 506, the computer recordable medium 508, and/orthe communications medium 510.

The non-transitory computer readable medium 506 can also be distributedamong multiple data storage elements, which could be remotely locatedfrom each other. The computing device that executes some or all of thestored instructions can be a microfabrication controller, or anothercomputing platform. Alternatively, the computing device that executessome or all of the stored instructions could be remotely locatedcomputer system, such as a server.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A method for fabricating a mountable device, themethod comprising: fabricating a bio-compatible structure that includesan electronic component and a conductive pattern, wherein the electroniccomponent has a first surface and a second surface opposite the firstsurface and includes electrical contacts on the second surface, whereinfabricating the bio-compatible structure comprises: forming a firstlayer of a bio-compatible material; positioning the first surface of theelectronic component on the first layer of the bio-compatible material;forming a second layer of the bio-compatible material over the firstlayer of the bio-compatible material and the second surface of theelectronic component; exposing the electrical contacts on the secondsurface of the electronic component by removing a portion of the secondlayer of the bio-compatible material; after exposing the electricalcontacts, forming the conductive pattern, wherein the conductive patterndefines sensor electrodes on the second layer of the bio-compatiblematerial and electrical interconnects between the sensor electrodes andthe electrical contacts; forming a third layer of the bio-compatiblematerial over the conductive pattern, wherein the third layer of thebio-compatible material includes a portion covering the sensorelectrodes; and exposing the sensor electrodes by removing the portionof the third layer of the bio-compatible material covering the sensorelectrodes; and surrounding the bio-compatible structure with a polymer,wherein the polymer defines at least one mounting surface of themountable device.
 2. The method of claim 1, wherein forming the firstlayer of the bio-compatible material comprises forming the first layerof the bio-compatible material on a working substrate.
 3. The method ofclaim 2, wherein fabricating the bio-compatible structure furthercomprises: after exposing the sensor electrodes, releasing the firstlayer of the bio-compatible material from the working substrate.
 4. Themethod of claim 1, wherein fabricating the bio-compatible structurefurther comprises: after exposing the sensor electrodes, annealing thefirst, second, and third layers of the bio-compatible material so thatthe layers are sealed together.
 5. The method of claim 4, wherein theannealing fully encapsulates the bio-compatible structure with thebio-compatible material, except for the sensor electrodes.
 6. The methodof claim 1, wherein removing the portion of the second layer of thebio-compatible material comprises: forming a masking layer on the secondlayer of the bio-compatible material, wherein the masking layer exposesthe portion of the second layer of the bio-compatible material; etchingthe portion of the second layer of the bio-compatible material exposedby the masking layer to provide a remaining portion of the second layerthat is covered by the masking layer; and removing the masking layerfrom the remaining portion of the second layer.
 7. The method of claim6, wherein the remaining portion of the second layer of thebio-compatible material is substantially flush with the second surfaceof the electronic component.
 8. The method of claim 1, wherein removingthe portion of the third layer of the bio-compatible material coveringthe sensor electrodes comprises: forming a masking layer on the thirdlayer of the bio-compatible material, wherein the masking layer exposesthe portion of the third layer of the bio-compatible material; etchingthe portion of the third layer of the bio-compatible material exposed bythe masking layer to provide a remaining portion of the third layer thatis covered by the masking layer; and removing the masking layer from theremaining portion of the third layer.
 9. The method of claim 8, whereinthe remaining portion of the third layer of the bio-compatible materialcovers all of the conductive pattern except for the sensor electrodes.10. The method of claim 1, wherein the sensor electrodes include aworking electrode, a reference electrode, and a counter electrode of anelectrochemical sensor.
 11. The method of claim 10, wherein fabricatingthe bio-compatible structure further comprises: forming a reagent layerproximal to the sensor electrodes.
 12. The method of claim 1, whereinthe electronic component further includes additional electrical contactson the second surface, and wherein the conductive pattern furtherdefines an antenna on the second surface of the bio-compatible materialand electrical interconnects between the antenna and the additionalelectrical contacts.
 13. The method of claim 1, wherein thebio-compatible structure is ring shaped.
 14. The method of claim 1,wherein the bio-compatible material comprises parylene.
 15. The methodof claim 1, wherein the mountable device is an eye-mountable device, andwherein the polymer defines a concave surface configured to mount themountable device on a corneal surface and a convex surface configured tobe compatible with eyelid movement when the concave surface is somounted.